Field of the Invention
The invention concerns a method for operating a temperature control apparatus for a medical examination apparatus, in particular magnetic resonance apparatus, wherein the medical examination device causes a heat input into the body of a patient to be examined during an examination procedure, and the temperature control apparatus has at least one temperature modifier designed to change the temperature of the patient. The invention also concerns a temperature control apparatus, a medical examination apparatus embodying such a temperature control apparatus, and a non-transitory, computer-readable data storage medium encoded with programming instructions that cause such a method to be implemented.
Description of the Prior Art
As is known, in some cases an energy input into the body of a patient occurs when an examination is carried out with a medical examination device, and this can lead to an increase in the patient's trunk temperature. If the medical examination device is a magnetic resonance apparatus, voltages are induced due to the magnetic fields generated during an examination procedure, which voltages can generate an electrical flow of current that heats the body of the patient. Magnetic resonance apparatuses are therefore always designed such that this kind of heating is limited. Limiting such heating also is covered by relevant standards (e.g. TEC 60601-2-33).
The generated heat is dissipated from the body of the patient to the patient's surroundings by convection, thermal radiation and by cooling through evaporation due to the transpiration of the patient that occurs. If these heat loss mechanisms are not enough to dissipate the heat output that occurs during the examination procedure, the trunk temperature of the patient increases. Since the patient frequently reacts with discomfort to an increase of this kind. Standards likewise provide that the increase in the trunk temperature should be limited to a maximum of one degree Celsius. However, the trunk temperature is not generally directly accessible to a measurement and cannot be indirectly determined with sufficient accuracy. It is also known to estimate the trunk temperature by taking into account the specific absorption rate during an examination with a magnetic resonance apparatus, for which purpose an examination interval of six minutes is typically considered. To improve heat loss it is also known to reduce the temperature of the surroundings in which the magnetic resonance apparatus is operated and in which the patient is located. This approach, however, frequently leads to the patient being cold.
It is also known to use fans that cool the patient during the examination procedure. DE 10 2008 010 937 A1 discloses a cooling device for air conditioning an examination room of a medical examination device having a temperature detection device, an air conditioning system for generating conditioned air and an air outlet system arranged inside the examination room. A control unit is provided that controls the air conditioning system on the basis of data detected by the temperature detection device.
A ventilation unit for a magnetic resonance system is known from US 2014/0103930 A1, which has a ventilator. Its operating parameters are controlled as a function of a heat signal that describes a change in heat of an examination subject. In particular, the specific absorption rate can be considered in this connection. Methods of this kind do not take into account the heat loss by the patient to the surroundings, however.
A magnetic resonance apparatus with at least one cooling unit having a cooling pad is known from US 2014/0249401 A1, wherein a control unit is designed to control operation of the cooling unit during an examination as a function of a detected or anticipated temperature of an examination subject. It has been found, however, that a surface-measured or estimated temperature of the patient is a poor indicator of the patient's thermal well-being. Skin temperature, for example, reacts only very slowly to a change in the trunk temperature.